1. Field of the Invention
The present invention relates to a curable epoxy resin composition. More particularly, the invention relates to a one-pack, thermosetting epoxy resin composition having an excellent storage stability and curable at a relatively low temperature in a short time.
Further, the present invention relates to a curable epoxy resin composition containing a curing agent highly compatible with an ordinary epoxy resin to form a cured product having excellent mechanical strength, adhesiveness and water resistance.
2. Prior Art
The development of a latent curing epoxy resin composition of one-pack type usable as an adhesive for structural materials has been demanded. In processes proposed heretofore, an imidazole compound or its salt with an acid is used as a curing agent.
However, the conventional curing epoxy resin compositions of one-pack type have problems that heating at a high temperature for a long time is required and that the storage stability thereof is yet unsatisfactory, since the curing reaction proceeds at room temperature due to their insufficient latentness even though they can be cured at a relatively low temperature. The shelf life of them is usually only about 10 to 20 days at room temperature. Under these circumstances, an improvement has been demanded.
Another defect is that when they are cured at a relatively low temperature in a short time, the cured product has a quite low peeling strength.
To overcome these defects, a curing agent comprising a dialkylamine to which an epoxy resin is added is disclosed in the specifications of Japanese Patent Laid-Open Nos. 155222/1981 and 100127/1982 and a curing agent comprising an amino alcohol or aminophenol to which an epoxy resin is added is disclosed in the specification of Japanese Laid-Open No. 53526/1984.
However, when the above-mentioned curing agents are used, the compatibility thereof with the epoxy resin is poor and it is difficult to control the balance among heat resistance, flexibility and adhesiveness of the obtained cured product, since no active hydrogen of the amino group is contained in the molecule.